Anticyclonic Rotation Research Articles

The vortex created by mass transfer between layers of a rotating fluid

Abstract A simple way to model stratification of the ocean or atmosphere is in terms of two superposed homogeneous layers of different density. Effects of cooling of the upper layer, such as that which occurs during bottom-water formation in the ocean, can be simulated by mass transfer from the upper layer to the lower layer. A model is constructed to see What effect such a mass transfer has on the flow when the mass transfer is confined to a limited region. The main effects are (i) doming of the interface, which maintains pressure gradients in balance with the velocity field, (ii) cyclonic rotation in the upper layer due to conservation of angular momentum of particles king drawn toward the sink, yet anticyclonic vorticity for those particles outside the mass transfer region due to shrinking of vortex lines drawn up over the dome. (iii) generally anticyclonic rotation in the lower layer due to particles tending to maintain their angular momentum while being pushed outwards, but some cyclonic rotation nea...

Observation of inertial waves in the stratosphere

A series of radiosonde flights over Laverton, Victoria (38°S), is found to have sufficient vertical (100m) and temporal (3 h) resolution, and sufficient length (28 days) to detect inertial waves. Fourier analysis shows that in the stratosphere there is a strong anticyclonic rotation of the wind vector which has energy concentrated near the local inertial frequency. This rotation is associated with a vertical wavelength between 1 and 3 km, and a downward phase propagation. There is no sign of inertial waves in the troposphere. The waves appear to be generated below the stratosphere and spread upwards.

Observation of inertial waves in the stratosphere

AbstractA series of radiosonde flights over Laverton, Victoria (38°S), is found to have sufficient vertical (100m) and temporal (3 h) resolution, and sufficient length (28 days) to detect inertial waves. Fourier analysis shows that in the stratosphere there is a strong anticyclonic rotation of the wind vector which has energy concentrated near the local inertial frequency. This rotation is associated with a vertical wavelength between 1 and 3 km, and a downward phase propagation. There is no sign of inertial waves in the troposphere. The waves appear to be generated below the stratosphere and spread upwards.

Continental Shelf Waves in the Florida Straits

Abstract Current measurements from three stations along the east coast of Florida at about 300 m water depth with a maximum longshore separation of 180 km were used to analyze for the presence of propagating waves. The analysis was done by solving the inverse problem of determining the most likely wave parameters from 36 independent auto spectra and cross spectra from four current meters. For the 10–13 day band a significant fit of the data by a wave cross-spectral function was found. The wavelength is 170 km and the phase propagation 17 cm s−1 toward the south. The current fluctuations are elliptically polarized with anti-cyclonic rotation and with an axis ratio of 0.30. The mean current amplitude is 14.3 cm s−1. A marginally significant fit with similar wave parameters resulted for the 7–10 day band. The results suggest that these waves are continental shelf waves, probably generated by atmospheric cold front passages.

Some mechanisms of oceanic mixing revealed in aerial photographs

Estimates of circulation rates within the mixed layer of the ocean have been made based on aerial photographs of a variety of dye injections and floating cards in the surface and near-surface levels under different wind, sea state, and thermal profile conditions. The following are the main features derived from our studies of the circulation patterns in the mixing layer in the Bermuda area. (1) Except under calm conditions, the first few meters of the sea are subjected to helical flow of small-size Langmuir cells with 3 to 6 meter spacing between the convergence lines. (2) Under moderate to strong wind conditions (10–30 knots), a hierarchy of larger-size Langmuir cells is developed. The maximum horizontal spacing between the larger cells is approximately the same as the depth of the mixing layer. The spacing of the convergence zones between the largest cells was 280 meters, and they were accompanied by medium and small-size cells of approximately 35 and 5 meters, respectively. Estimates of the apparent vertical diffusion associated with the large and medium Langmuir cells are thousands and hundreds of cm2/sec, respectively. (3) A stratified flow resembling an Ekman spiral is observed under moderate conditions. (4) There is coexistence between the small-size Langmuir cells and the Ekman spiral below. However, when the large Langmuir cells are developed, the flow pattern in the mixing layer does not resemble an Ekman spiral. The transition from the Ekman to the Langmuir regime occurs with turbulence Reynolds numbers of approximately 100. (5) Under calm conditions following a period of moderate winds and thermal instability, we observed convergence zones having anticyclonic rotation with inertial period.

ON THE OCCURRENCE OF DYNAMIC INSTABILITY IN INCIPIENT AND DEVELOPING HURRICANES

Abstract Observations made by the specially instrumented aircraft, operated by the National Hurricane Research Project, establish the occurrence of dynamic instability, notably in the form of anomalous winds in the upper troposphere above hurricane Daisy, shortly after its inception. It is inferred that the dynamic instability released by these anomalous winds, which represent anticyclonic rotation in space, triggered Daisy's development. Since the observed dynamic instability occurred on a mesoscale, the above inference is not amenable to direct verification from synoptic maps. However, synoptic conditions favorable for the development of anomalous winds are discussed and it is found that these conditions prevailed in the upper troposphere directly above Daisy and Gracie a short time before they reached hurricane intensity. The role of negative absolute vorticity is shown to vary. In the presence of anomalous winds it is a stabilizing factor which is nonetheless important in channeling outflow at the top...

THE OCCURRENCE OF ANOMALOUS WINDS AND THEIR SIGNIFICANCE

Abstract Observational evidence is provided for the occurrence of anomalous winds which represent an anticyclonic rotation in space, and a mechanism for their development is suggested. The unstable nature of these winds and the role they play in the development of certain types of atmospheric disturbances is then discussed, and it is suggested that anomalous winds provide the dynamic mechanism for triggering hurricane formation and for the observed deepening of troughs downstream from intense pressure ridges. Finally it is noted that although the observational evidence presented is for the occurrence of anomalous winds over small regions of the atmosphere, their development is dependent on large-scale processes and their effect extends beyond the area where they occur.

A NON-TORNADIC SPIRAL-SHAPED RADAR ECHO1

Abstract A spiral-shaped radar echo, apparently of non-tornadic origin, was observed over southwestern Alabama on the afternoon of July 1, 1959. A series of scope photographs of the CPS-9 radar at Maxwell Air Force Base shows that this feature persisted for well over an hour and suggests that the pattern was experiencing anticyclonic rotation.

A Common Wind Damage Pattern in Relation to the Classical Tornado

A wind damage pattern in which no major damage has been accomplished by winds blowing toward the direction from which the storm came can result from a classical tornado if the speed of translation is high enough relative to the maximum wind speed. A distinct rotary damage pattern indicates that the speed of translation is a less important component of the total speed. One might consider a wind damage pattern in which there is,An increase in damage intensity from right to left,No major damage accomplished to the left of the line of most extreme damage, andEvidence indicating that the damage in the major damage area was accomplished by winds blowing with the direction of translation of the storm, to be a point in favor of cyclonic rotation. If the build-up were from left to right, with the break-off to the right of the line of most extreme damage, the point would be in favor of anti-cyclonic rotation. The wind speed-wind pressure relationship is discussed briefly, and tables and graphs showing the wind speeds and pressures at points on opposite sides of a tornado, for assigned values of the speeds of rotation and translation, are included. A table estimating the total force on a wall resulting from assumed wind speeds is also presented.

塵旋風に就て(第一稿)

The author, meteorologist at the Military Aeronautical College at Tokorozawa near Tokyo, very often observed dust storms with interest, occurring there during recent ten years. He already contributed the reports in them twice to this Journal. In the present paper he classides the dust storm into the following three classes:- The first class, Funnel, shaped or smork column type. Most frequent, average height is 50cm; diameter near the ground is about 2 to 10 metres, duration of existence, 5 minute to quater an hour; sense of revolution is sometimes right and sometimes left. The s_??_cond class, Cylind_??_cal type; rather frequent, so-called dust devil in India; several columns with diameters of a few metres appear at the same time reaching the height about 300-600m. Their colour is dark; they have sharp, well defined edges at their middle parts, while rather diffused rims at their tops and feet. Their existing duration is about 10 minutes, after dissolving of the columns dust smork is still seen above the sky for some thirty minutes. Plate 13. shows “Dust devil” and Funnel shaped one. The third class, Group type: many whirls revolve round along one and the same circular orbit; the sense of revolution is the same as that of the rotation of each whirl.The author noticed the sudden change of the sense of rotation of a whirl as Dr. E. H. Hankin(1) has formerly remarked. He observed it at the distance of about 4 metres. At first the rotation was of cyclonic sense, then suddenly it changed to anticyclonic and after about one minute the original rotation is resumed. Then the whirl seemed hesitating to rotate and all the sudden the anticyclonic rotation started again when the whirl displaced about 4 or 5 metres. After a while it vanished. The author hardly believe that he saw an ilusion. An aviator in the college once got into such a dust devil at the height of 400 meters. (March 13, 1924). All the radders of his machine fell off and he lost control of it. For a while came back again the resistance on radders and he was safe. The author once ventured to walk into the dust storm. He felt some lift with his body. He estimated the wind velocity at 30m/s. People in this vicinity sometimes were injured in the dust storm, which perhaps due to the sudden fall of pressure of some 5 or 6mm of mercury. Once a dust storm passed on across a wcoden house at a corner of the Aerodrome. Windor panes were broken and fell outside. A part of the roof of the house was torn off.The progressive motion of the dust storm seems to be controlled by thegeneral flow of air at that place.It was known that dust storm sometimes accompani_??_s electric discharge. On March 19, 1924 an air-ship filled with hydrogen, somewhat old and impure, exploded. The day was especially marked with dust storm and the author believes that the airship, being painted with metalic powder, must have the same electric potential as_??_the surrounding air. On encountering a dust storm which ascended from the ground, the inevitable fate must be the electric discharge dué to the great potential differerence between the airship and the dust columns and consequent explosion of hydrogen.Meteorological conditions when the dust storm oceurs. The occurrence of the storm is confined in February, March and April. Two or three hours after the sunrise the storm begins to be formed and it is most vigorous at the noontide, and gradually subsides at the sunset. The dust-storm never occurs when it is raining. The humidity of air during the occurrence is very low, never exceeds 40%. On that occasion the wind velocity is always small, and temperature is rather high. The dust storm preferably occurs on a day of anticyclonic weather in which morning temperature is rather low which followed by a sudden rise caused by the solar radiation.